If lines k and j are in the xy–coordinate plane, is the slope of line k greater than the slope of line j ?

(1) The x-intercept of line k is greater than the x-intercept of line j

(2) Lines k and j intersect at (7, 2)
_________________

countdown-beginshas-ended-85483-40.html#p649902

Approach of economist is nice. Lets do it more mathematically.
1)insuff. No need to explain.
2)insuff. No need to explain.

together
line k=> y=mx+n
line j=> y=tx+y
we know from 1 that n is greater than y. And we know from 2 that they are intersecting at point (7,2).
That makes
2=7m+n
2=7t+y
7m+n=7t+y
7m+n<7t+n
7m<7t
m<t

SUFF.
C.

IMO E. We need more information to find the answer.

Yes....this is correct. But with a small correction.

Sorry to disappoint you guys, but seems that the answer should be E.

First of all to solve this question think that the best way is graphic approach:

We all agree that (1) and (2) alone are not sufficient.

Lets combine --> draw only X-axis. k intercept is greater than j intercept --> k intercept (k1) point right to j intercept point (j1) --> Interception of lines is above X-axis (point 7;2) --> it will give us only three possible ways to draw the lines:
A. j has negative slope, k has negative slope --> slope of k>slope of j, (because j is closer to vertical line);
B. j has positive slope, k has negative slope --> slope of k<slope of j;
C. j has positive slope, k has positive slope --> slope of k>slope of j, (because k is closer to vertical line);

So (1)+(2) not sufficient. Answer E.

BUT the way you were solving also should get E:

f(k)=mx+n
f(j)=tx+p
(1) The x-intercept of line k is greater than the x-intercept of line j --> 0=mx+n; 0=tx+p --> -n/m>-p/t or
n/m<p/t --> not sufficient;
(2) Lines k and j intersect at (7, 2)
2=7m+n; 2=7t+p --> 7m+n=7t+p -->not sufficient;

Combining the way you did:
n=2-7m --> n/m=2/m-7
p=2-7t --> p/t=2/t-7
n/m<p/t --> 2/m-7<2/t-7 --> 1/m<1/t --> (t-m)/mt<0
And here is the catch, from above statement you can not determine whether m>t or not. t=1<m=3 statement is true and t=1>m=-3 statement is also true.
Answer E.
_________________

PLEASE READ AND FOLLOW: 11 Rules for Posting!!!

RESOURCES: [GMAT MATH BOOK]; 1. Triangles; 2. Polygons; 3. Coordinate Geometry; 4. Factorials; 5. Circles; 6. Number Theory

COLLECTION OF QUESTIONS:
PS: 1. Tough and Tricky questions; 2. Hard questions; 3. Hard questions part 2; 4. Standard deviation; 5. Tough Problem Solving Questions With Solutions; 6. Probability and Combinations Questions With Solutions; 7 Tough and tricky exponents and roots questions; 8 12 Easy Pieces (or not?); 9 Bakers' Dozen; 10 Algebra set. NEW!!!

DS: 1. DS tough questions; 2. DS tough questions part 2; 3. DS tough questions part 3; 4. DS Standard deviation; 5. Inequalities; 6. 700+ GMAT Data Sufficiency Questions With Explanations; 7 Tough and tricky exponents and roots questions; 8 The Discreet Charm of the DS ; 9 Devil's Dozen!!!; 10 Number Properties set. NEW!!!


What are GMAT Club Tests?
25 extra-hard Quant Tests

Find out what's new at GMAT Club - latest features and updates

Hi Bunuel,

Request you to please look at the colored portion again and confirm if its correct. Isn't in Option A->Slope of j > Slope of K. If not, please provide your reasoning, may be I'm lacking some concept.

thanks
_________________

+1 Kudos me, Help me unlocking GMAT Club Tests